Solar Twin: A Star That Is Almost Identical To Our Sun

Astronomers discover a star that might have been born in the same stellar nursery as the Sun.

The age, carbon isotopes ratio and chemical abundances of this star are roughly same as the Sun.

Named HD 186302, the star is 184 light-years away from Earth.

Like most low-mass stars, our Sun probably formed in a cluster about 4.57 billion years ago. As per several theories, the Sun (along with the solar system) formed from the solar nebula – a huge, rotating cloud of dust and gas. As it collapsed (due to its own gravity), it spun faster and flattened into a disk.

Usually, open clusters last for approximately 200 million years, though it depends on the galaxy characteristics and the cluster mass. The cluster in which our Sun was born has long been dissipated, and its objects (solar siblings) are dispersed throughout the Milky Way galaxy.

Recently, an international team of astronomers used a novel technique to find these solar siblings, and luckily they discovered a star that might have been born in the same stellar nursery as the Sun. They are quite confident that it’s not only a solar sibling but more likely a solar twin.

Mirror Image

The near-identical star, named HD 186302, isn’t the first close relative of the Sun ever discovered. In 2014, another team of astronomer had found the first sibling, HD 162826, which is about 15% more massive and 3% more abundant in metals than our Sun.

The present research is a part of AMBRE project that aims to find the Sun’s ancient family. So far, astronomers have identified 17,000 stars using an array of spectrographs and data obtained from the European Space Agency’s Gaia space observatory. These data helped them identify chemical abundance, motions and ages of stars in our galaxy.

After carefully analyzing the celestial data, they found a main sequence star HD 186302: it’s nearly 184 light-years away and has an apparent magnitude (the measure of star’s brightness as seen from Earth) of 8.76.

The age, carbon isotopes ratio and chemical abundances of the star are roughly same as the Sun. Overall, the HD 186302 is the most precisely characterized and probably the most identical twin of our Sun.

HD 186302’s location (red circle) | Courtesy of researchers | ESA

These types of similarities could help researchers figure out what kind of environments sibling formed in, and image their now-defunct stellar nursery and other members that were formed inside it. Also, the data make astronomers wonder if the star could host habitable planets within its orbit.

Authors did mention that there is a very small probability that life extent from Earth to exoplanets (planets outside our solar system) during the heavy bombardment era. The HD 186302 could have a rocky-type planet in the habitable zone, and if this planet hosted any form of life, then we would have a Sun 2.0 with an Earth 2.0 revolving around it.

In the coming years, researchers will use ESO’s High Accuracy Radial velocity Planet Searcher (HARPS) and Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO) to monitor stars for orbiting planets.